Testing Pipelines

Every Acme pipeline can be tested locally before deployment. The acme test command validates your configuration, checks connections, and runs your pipeline against fixture data.

Why test?

Testing prevents:

• Schema mismatches that silently drop columns
• Transform logic errors that corrupt data
• Connection failures that only surface in production

Test types

1. Validation tests

Check that your YAML is valid and all referenced transforms exist:

acme test --validate pipelines/user-analytics.yml

✓ YAML syntax valid
✓ Source 'users_db' configuration complete
✓ Transform 'filter' has valid condition
✓ Transform 'python/hash_email' function found
✓ Destination 'bigquery/active_users' configuration complete
✓ All 5 checks passed

2. Fixture tests

Run your pipeline against local test data:

# tests/test_user_analytics.yml
pipeline: pipelines/user-analytics.yml

fixtures:
  users_db: tests/fixtures/sample_users.csv

assertions:
  - row_count: { min: 1, max: 100 }
  - columns:
      [id, full_name, email_hash, account_age_days, is_recent, created_at]
  - no_nulls: [id, full_name, email_hash]
  - unique: [id]

Create the fixture file:

id,email,first_name,last_name,status,created_at,last_login_at
1,alice@example.com,Alice,Johnson,active,2025-01-15,2026-02-10
2,bob@example.com,Bob,Smith,inactive,2024-06-01,2025-03-01
3,carol@example.com,Carol,White,active,2025-11-20,2026-02-14

Run the test:

acme test tests/test_user_analytics.yml

✓ Pipeline loaded: user-analytics
✓ Fixture loaded: sample_users.csv (3 rows)
✓ Source: users_db (3 rows extracted)
✓ Transform: filter → 2 rows (filtered 1 inactive)
✓ Transform: python/hash_email → 2 rows
✓ Transform: map → 2 rows (3 fields computed)
✓ Transform: select → 2 rows (6 columns)

Assertions:
  ✓ row_count: 2 (within 1-100)
  ✓ columns: all 6 present
  ✓ no_nulls: no null values found
  ✓ unique: id is unique

All tests passed!

3. Snapshot tests

Compare pipeline output against a known-good snapshot:

# Generate a snapshot
acme test tests/test_user_analytics.yml --update-snapshot

# Run against the snapshot
acme test tests/test_user_analytics.yml --snapshot

# .github/workflows/test.yml
- name: Test pipelines
  run: acme test tests/

Writing good tests

1. Test edge cases — empty datasets, null values, special characters
2. Test transforms individually — isolate complex transforms with targeted fixtures
3. Test schema evolution — what happens when a source adds or removes a column?
4. Keep fixtures small — 5-20 rows is usually enough

Related

• Your First Pipeline — build a pipeline to test
• Deployment — CI/CD integration
• Error Handling — handling unexpected data